Android :: Method OnBackPressed() Of Type FirstGroup Must Override Superclass Method

I'm trying to override the onBackPressed() method of the ActivityGroup class:

public class MyClass extends ActivityGroup {

@Override
public void onBackPressed() {
// do something
return;
}

but I'm getting the error The method onBackPressed() of type MyClass must override a superclass method. I'm relatively new to Java, I've seen here that people do it and it works for them Why I'm getting this error? I'm writing an app for android 1.5, could the problem be here?